Tunable Afterglow Luminescence and Triple-mode Emissions of Thermally Activated Carbon Dots Confined within Nanoclay
Carbon dots (CDs) as newly emerged afterglow materials have attracted extensive interests owing to their numerous merits (e.g., such as low toxicity, excellent biocompatibility, low cost and facile preparation.), yet most CDs are generally restricted to dual-mode emissions (such as blue fluorescence and green phosphorescence). Herein, we provide a facile and universal approach to achieve the tunable afterglow luminescence and the interesting multi-mode emissions (fluorescence (FL), delayed fluorescence (DF), and room-temperature phosphorescence (RTP)) through situ formating and covalently fixing carbon dots (CDs) on the layer of clay (CDs@clay) induced by thermal-treatment. The multi-mode emissions are mainly activated by the n → π* transitions of C=O groups and the covalent bond formation between CDs and clay sheets. It is noteworthy that the afterglow emissions (DF and RTP) switching can be achieved via excitation wavelengths and temperature variation, which strongly depend on whether the electrons are directly excited to the excited state S2 or S1 state. Such the excellent properties make CDs@clay have important application in advanced multicolor-encoded and multiple-mode-integrated optical anti-counterfeiting and sensing field.